Communication method, aggregation unit, distribution unit, mobile communication system, chip set, and program

Abstract

This communication method, which is used in a communication system for providing a multicast / broadcast service (MBS), includes a step in which an aggregation unit included in a base station transmits MBS-related information to a distribution unit included in the base station on a network interface between the aggregation unit and the distribution unit. The MBS-related information relates to a user device receiving or interested in receiving an MBS service provided by a secondary cell under the distribution unit.

Description

[Technical Field]

[0001] The present disclosure relates to a communication method, an aggregation unit, and a distribution unit for use in a mobile communication system. [Background technology]

[0002] The 3GPP (3rd Generation Partnership Project) has defined technical specifications for NR (New Radio), a fifth-generation (5G) radio access technology. Compared to LTE (Long Term Evolution), a fourth-generation (4G) radio access technology, NR offers higher speed, larger capacity, higher reliability, and lower latency. 3GPP has also defined technical specifications for 5G / NR multicast / broadcast services (MBS) (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP Technical Specification: TS 38.300 V17.1.0 Summary of the Invention

[0004] A communication method according to a first aspect is a communication method for use in a mobile communication system providing a multicast / broadcast service (MBS), comprising a step of an aggregation unit included in a base station transmitting MBS-related information to a distributed unit included in the base station over a network interface between the aggregation unit and the distributed unit, the MBS-related information being information about user equipment receiving or interested in receiving an MBS service provided in a secondary cell under the control of the distributed unit.

[0005] According to a second aspect, an aggregation unit is included in a base station in a mobile communication system that provides a multicast / broadcast service (MBS), and includes a transmitter that transmits MBS-related information to a distributed unit included in the base station over a network interface between the aggregation unit and the distributed unit, the MBS-related information being information about user devices that are receiving or interested in receiving an MBS service provided in a secondary cell under the control of the distributed unit.

[0006] A distributed unit according to a third aspect is a distributed unit included in a base station in a mobile communication system that provides a multicast / broadcast service (MBS), and includes a receiving unit that receives MBS-related information from an aggregation unit included in the base station over a network interface between the aggregation unit and the distributed unit, the MBS-related information being information about user equipment receiving or interested in receiving an MBS service provided in a secondary cell under the control of the distributed unit. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. [Figure 2] 1 is a diagram illustrating a configuration of a UE (user equipment) according to an embodiment. [Figure 3] A diagram showing the configuration of a gNB (base station) according to an embodiment. [Figure 4] FIG. 10 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data. [Figure 5] FIG. 1 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals). [Figure 6] FIG. 1 is a diagram for explaining an outline of an operation of a mobile communication system according to an embodiment. [Figure 7] FIG. 2 is a diagram illustrating a first operation example of the mobile communication system according to the embodiment. [Figure 8] FIG. 10 is a diagram illustrating a second operation example of the mobile communication system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0009] (1) Configuration of mobile communication system FIG. 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. The mobile communication system 1 conforms to the 3GPP standard 5th Generation System (5GS). In the following description, 5GS is used as an example, but the mobile communication system may also be at least partially applied to an LTE (Long Term Evolution) system. The mobile communication system may also be at least partially applied to a 6th Generation (6G) system.

[0010] The mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20. Hereinafter, the NG-RAN 10 may be simply referred to as the RAN 10. The 5GC 20 may be simply referred to as the core network (CN) 20.

[0011] The UE 100 is a mobile wireless communication device. The UE 100 may be any device used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone) and / or a tablet terminal, a laptop PC, a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0012] The NG-RAN 10 includes a base station (called "gNB" in the 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, etc. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource that performs wireless communication with a UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0013] In addition, gNBs can also connect to the Evolved Packet Core (EPC), which is the LTE core network. LTE base stations can also connect to 5GC. LTE base stations and gNBs can also be connected via a base station-to-base station interface.

[0014] The 5GC20 includes an Access and Mobility Management Function (AMF) and a User Plane Function (UPF) 300. The AMF performs various mobility controls for the UE 100. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0015] 2 is a diagram showing the configuration of a UE 100 (user equipment) according to an embodiment. The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit that performs wireless communication with the gNB 200.

[0016] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 130.

[0017] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0018] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer, which will be described later. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processes by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0019] 3 is a diagram showing the configuration of a gNB 200 (base station) according to an embodiment. The gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240. The transmitter 210 and the receiver 220 constitute a wireless communication unit that performs wireless communication with the UE 100. The backhaul communication unit 240 constitutes a network communication unit that performs communication with the CN 20.

[0020] The transmission unit 210 performs various transmissions under the control of the control unit 230. The transmission unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0021] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 230.

[0022] The control unit 230 performs various controls and processes in the gNB 200. Such processes include processes for each layer, which will be described later. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processes by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0023] The backhaul communication unit 240 is connected to neighboring base stations via an Xn interface, which is an interface between base stations. The backhaul communication unit 240 is connected to the AMF / UPF 300 via an NG interface, which is an interface between a base station and a core network. Note that the gNB 200 may be configured (i.e., functionally divided) with a CU (Central Unit) and a DU (Distributed Unit), and both units may be connected via an F1 interface, which is a fronthaul interface.

[0024] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0025] The user plane radio interface protocol includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0026] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on a physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has CRC parity bits scrambled by the RNTI added.

[0027] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE100 and the MAC layer of gNB200 via transport channels. The MAC layer of gNB200 includes a scheduler, which determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE100.

[0028] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via logical channels.

[0029] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0030] The SDAP layer maps IP flows, which are the units for Quality of Service (QoS) control by the core network, to radio bearers, which are the units for QoS control by the Access Stratum (AS). Note that if the RAN is connected to the EPC, SDAP is not necessary.

[0031] FIG. 5 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals).

[0032] The protocol stack of the radio interface of the control plane has a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) layer instead of the SDAP layer shown in FIG.

[0033] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in an RRC inactive state.

[0034] The NAS layer, which is located above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMF 300A. Note that the UE 100 has an application layer and the like in addition to the radio interface protocol. Also, a layer lower than the NAS layer is referred to as an AS layer.

[0035] (2) Overview of MBS The mobile communication system 1 can perform resource-efficient distribution by using a multicast / broadcast service (MBS).

[0036] In the case of a broadcast communication service (also referred to as "MBS broadcast"), the same service and the same specific content data are simultaneously provided to all UEs 100 in a geographical area. That is, all UEs 100 within the broadcast service area are authorized to receive the data. The broadcast communication service is delivered to the UEs 100 using a broadcast session, which is a type of MBS session. The UEs 100 can receive the broadcast communication service in any of the following states: RRC idle state, RRC inactive state, and RRC connected state.

[0037] In the case of a multicast communication service (also referred to as "MBS multicast"), the same service and the same specific content data are provided simultaneously to a specific set of UEs. That is, not all UEs 100 within a multicast service area are permitted to receive the data. The multicast communication service is delivered to the UEs 100 using a multicast session, which is a type of MBS session. The UEs 100 can receive the multicast communication service in the RRC connected state using mechanisms such as Point-to-Point (PTP) and / or Point-to-Multipoint (PTM) delivery. The UEs 100 may also receive the multicast communication service in the RRC inactive (or RRC idle) state.

[0038] In the following, MBS broadcast will be mainly described, however, the embodiment is not limited to MBS broadcast and can be applied to MBS multicast.

[0039] A UE 100 in an RRC idle state, an RRC inactive state, or an RRC connected state receives MBS configuration for a broadcast session (e.g., parameters required for MTCH reception) via the MCCH. The parameters required for MCCH reception (MCCH configuration) are provided via system information. Specifically, System Information Block Type 20 (SIB20) includes the MCCH configuration. SIB Type 21 includes information on service continuity for MBS broadcast reception. The MCCH provides a list of all broadcast services, including ongoing sessions, transmitted on the MTCH. The broadcast session-related information includes the MBS session ID, associated G-RNTI scheduling information, and information on neighboring cells providing a specific service on the MTCH.

[0040] To ensure service continuity for MBS broadcast, the UE 100 in the RRC Connected state can send an MBS Interest Indication (MII) message, which is an RRC message, to the gNB 200 providing the SIB 21, including the following information: A list of MBS frequencies that the UE is interested in receiving Priority between receiving all listed MBS frequencies and receiving unicast bearers · A list of MBS broadcast services (service IDs) that the UE 100 is interested in receiving (if a SIB20 is scheduled on the UE's 100's PCell).

[0041] Note that the transmission of MBS Interest Indication messages can be implicitly enabled / disabled by the presence of SIB21.

[0042] When gNB200 provides RRC configuration and / or downlink allocation to UE100, it enables UE100 to receive MBS services in which UE100 is interested based on the MBS Interest Indication message.

[0043] (3) Overview of Carrier Aggregation In the embodiment, the UE 100 is configured with carrier aggregation (CA) by the gNB 200. In CA, multiple component carriers (CCs) corresponding to multiple serving cells are aggregated, and the UE 100 can simultaneously receive or transmit using the multiple CCs. The multiple CCs may be contiguous in the frequency direction. The multiple CCs may also be discontinuous.

[0044] When CA is configured, the UE 100 has only one RRC connection with the network (e.g., gNB 200). During RRC connection establishment / re-establishment / handover, one serving cell provides NAS mobility information, and during RRC connection re-establishment / handover, one serving cell provides security input. The one serving cell is called a primary cell (PCell). The primary cell is an MCG cell operating on a primary frequency where the UE 100 performs the initial connection establishment procedure or initiates the connection re-establishment procedure. If the UE 100 receives an RRC Setup message from a cell during the initial connection establishment procedure, the UE 100 considers the cell as the primary cell. A set of serving cells can be formed by configuring a secondary cell (SCell) together with a PCell for the UE 100. Therefore, the set of serving cells configured for the UE 100 consists of one PCell and one or more SCells. Reconfiguration, addition, and deletion of SCells can be performed by RRC.

[0045] To enable the power consumption of the UE 100 to be reduced when CA is configured, a cell activation / deactivation mechanism is supported. When an SCell is deactivated, the UE 100 does not need to receive the corresponding PDCCH or PDSCH, and does not need to perform the corresponding uplink and / or CQI measurements. On the other hand, when an SCell is active, the UE 100 can receive the PDSCH and PDCCH and perform CQI measurements.

[0046] If one or more SCells are configured in the UE 100, the gNB 200 can activate and deactivate the configured SCells. When an SCell is configured, it is deactivated unless the RRC parameter "sCellState" is set to active for the SCell. The configured SCells are activated and deactivated in the following manner: UE 100 receives SCell Activation / Deactivation MAC CE from gNB 200 The gNB 200 sets the RRC parameter "sCellDeactivationTimer" timer for each configured SCell. The UE 100 deactivates the corresponding SCell when the timer expires. The gNB 200 sets the RRC parameter "sCellState" for each configured SCell. If the parameter is set, the UE 100 activates the corresponding SCell at the time of SCell configuration.

[0047] The UE 100 can receive the MBS broadcast data and the MCCH from the PCell or one SCell at a certain timing. Note that UE-dedicated RRC signaling may be used to provide the SIB 20 of the SCell.

[0048] (4) Operation of the mobile communication system FIG. 6 is a diagram for explaining an outline of the operation of the mobile communication system 1 according to the embodiment.

[0049] In the embodiment, the gNB 200 is functionally divided into a central unit (CU) 250 and a distributed unit (DU) 260. While Fig. 6 shows an example in which the number of DUs 260 is one, the number of DUs 260 may be two or more. Each of the CU 250 and the DU 260 may have a hardware configuration as shown in Fig. 3.

[0050] The CU 250 is a logical node that includes the RRC, SDAP, and PDCP layers (protocols) of the gNB 200. The CU 250 controls the operation of the DU. The CU 250 is connected to the DU 260 via an F1 interface, which is a fronthaul interface. The CU is connected to neighboring base stations via an Xn interface, which is an interface between base stations.

[0051] The DU 260 is a logical node including the RLC, MAC, and PHY layers (protocols) of the gNB 200. The DU 260 forms one or more cells. In Fig. 6, an example is shown in which the cells formed by the DU 260, specifically, there are two cells (cell C1 and cell C2) under the control of the DU 260, but there may be two or more cells under the control of the DU 260.

[0052] In such an operating scenario, assume that UE 100, for which carrier aggregation is configured by gNB 200, is receiving or is interested in receiving an MBS service (e.g., an MBS broadcast) provided in cell C2, where cell C1 is the PCell of UE 100 and cell C2 is the SCell of UE 100.

[0053] As described above, the gNB 200 can activate / deactivate an SCell by transmitting an SCell Activation / Deactivation MAC CE to the UE 100. Since the MAC layer is included in the DU 260, the DU 260 transmits the SCell Activation / Deactivation MAC CE to the UE 100.

[0054] However, since the MII message is an RRC message and is transmitted from the UE 100 to the CU 250 on the RRC layer, the DU 260 cannot grasp the contents of the MII message. Therefore, the DU 260 cannot grasp that the UE 100 is receiving or is interested in receiving the MBS broadcast provided by the cell C2. Therefore, the DU 260 may deactivate the SCell by transmitting an SCell Deactivation MAC CE to the UE 100. When the SCell is deactivated, there is a problem that the UE 100 cannot receive the MBS broadcast provided by the cell C2. Furthermore, such a problem may occur not only in the case of an MBS broadcast but also in the case of an MBS multicast.

[0055] Therefore, in the embodiment, the CU 250 transmits MBS-related information to the DU 260 over the F1 interface between the CU 250 and the DU 260. The MBS-related information is information about the UE 100 that is receiving or has an interest in receiving an MBS service (e.g., MBS broadcast) provided in an SCell (cell C2) under the control of the DU 260. This enables the DU 260 to activate / deactivate the SCell taking into account the MBS interest of the UE 100, thereby improving service continuity in the UE 100. Note that in the embodiment, the term "MBS service" mainly refers to an MBS broadcast, but may also refer to an MBS multicast.

[0056] The CU 250 may send a UE Context Setup Request message including MBS-related information or a UE Context Modification Request message including MBS-related information to the DU 260. These messages are F1 messages associated with the UE 100 and are suitable for transmitting MBS-related information.

[0057] The CU 250 receives an MBS interest indication (MII), which is an RRC message, from the UE 100. The CU 250 transmits MBS-related information to the DU 260 based on the MBS interest indication (MII).

[0058] The DU 260 determines activation and deactivation of the SCell for the UE 100 based on the MBS-related information received from the CU 250. The DU 260 may transmit, to the UE 100, an SCell Activation / Deactivation MAC CE, which is a Medium Access Control Element (MAC CE) indicating an instruction to activate or deactivate the SCell, according to the result of the determination.

[0059] In an embodiment, the MBS-related information transmitted from the CU 250 to the DU 260 may be information indicating whether or not to request activation of an SCell. The MBS-related information may include information indicating the reason for the request.

[0060] The MBS-related information sent from CU250 to DU260 is Information indicating the MBS service that the UE 100 is receiving or is interested in receiving (for example, a service ID such as TMGI), Information indicating the MBS frequencies that the UE 100 is receiving or is interested in receiving; and Information about the cell providing the MBS service or MBS frequency (e.g., cell ID) It may include at least one of the following.

[0061] 7 is a diagram showing a first operation example of the mobile communication system 1 according to the embodiment. In this operation example, the CU 250 transmits at least a part of the MII received from the UE 100 to the DU 260 as MBS-related information.

[0062] In step S101, the UE 100 is receiving or is interested in receiving an MBS service (eg, an MBS broadcast) provided in a cell C2 (SCell).

[0063] In step S102, UE 100 transmits MII to CU 250. As described above, MII includes information on MBS services of interest (TMGI), information on MBS frequencies of interest, and information on unicast and MBS reception priority. CU 250 receives the MII. Note that in the case of MBS multicast, CU 250 may receive information included in the MII from the core network instead of receiving the MII from UE 100.

[0064] In step S103, the CU 250 transmits a UE Context Setup Request message or a UE Context Modification Request message including MBS-related information to the DU 260 over the F1 interface. The MBS-related information includes information on MBS services of interest to the UE 100 (TMGI) and / or information on MBS frequencies of interest to the UE 100. The MBS-related information may include a cell ID and / or a frequency identifier of a cell (cell C2) that provides an MBS service of interest to the UE 100. Alternatively, the MBS-related information may include a cell ID and / or a frequency identifier of a cell that should not be deactivated (i.e., should remain active) because the UE 100 is interested in receiving MBS.

[0065] In step S104, the DU 260 identifies a cell C2 (SCell) that provides an MBS service of interest to the UE 100 based on the MBS-related information from the CU 250. The DU 260 may identify a cell (SCell) that does not provide an MBS service of interest to the UE 100. The DU 260 may identify a cell (SCell) that provides an MBS service that the UE 100 is no longer interested in. The DU 260 determines activation / deactivation of the SCell.

[0066] In step S105, the DU 260 transmits an SCell Activation / Deactivation MAC CE to the UE 100 as necessary. Here, the DU 260 activates the cell C2 (SCell) that provides the MBS service that the UE 100 is interested in. The DU 260 may activate / deactivate an SCell that does not provide the MBS service that the UE 100 is interested in, depending on the traffic situation of unicast transmission. Here, the description will proceed assuming that the DU 260 instructs the UE 100 to activate the cell C2 (SCell).

[0067] In step S106, the UE 100 activates the cell C2 (SCell) in response to the instruction from the DU 260 in step S105.

[0068] After that, in step S107, it is assumed that the UE 100 is no longer interested in the MBS service (eg, MBS broadcast).

[0069] In step S108, the UE 100 notifies the CU 250 by using the MII that the UE 100 is no longer interested in the MBS service. In the case of MBS multicast, the CU 250 may receive information indicating that the UE 100 is no longer interested in the MBS service from the core network.

[0070] In step S109, the CU 250 transmits a UE Context Setup Request message or a UE Context Modification Request message including MBS-related information reflecting the MII in step S108 to the DU 260. The message may include information on cells that can be deactivated (are allowed to be deactivated).

[0071] In step S110, the DU 260 determines whether to deactivate the cell C2 (SCell), based on the MBS-related information from the CU 250. Here, the description will proceed assuming that it is determined to deactivate the cell C2 (SCell).

[0072] In step S111, the DU 260 transmits an SCell Deactivation MAC CE to the UE 100.

[0073] In step S112, the UE 100 deactivates the SCell in response to the reception of the SCell Deactivation MAC CE in step S111.

[0074] 8 is a diagram showing a second operation example of the mobile communication system 1 according to the embodiment. In this operation example, the CU 250 transmits a request based on the MII received from the UE 100 to the DU 260. Operations that overlap with those in the first operation example described above will not be described again.

[0075] In step S201, the UE 100 is receiving or is interested in receiving an MBS service (eg, an MBS broadcast) provided in a cell C2 (SCell).

[0076] In step S202, the UE 100 transmits the MII to the CU 250. In the case of MBS multicast, the CU 250 may receive information included in the MII from the core network instead of receiving the MII from the UE 100.

[0077] In step S203, the CU 250 identifies an SCell that provides the MBS service based on the MII (or information received from the core network). Here, it is assumed that the CU 250 determines that the identified SCell is in an inactive state.

[0078] In step S204, the CU 250 sends a UE Context Setup Request message or a UE Context Modification Request message to the DU 260, the UE Context Setup Request message including MBS-related information indicating a request for SCell activation to the DU 260. The cell ID of the cell to activate Cause: Information indicating that the UE 100 is interested in receiving an MBS service (e.g., an MBS broadcast) TMGI: Identifier indicating the MBS service to which SCell activation is applied MBS frequency: an identifier indicating the frequency on which the UE 100 is interested in receiving MBS services (e.g., MBS broadcasts) It includes at least one of the following:

[0079] In step S205, the DU 260 activates (or maintains the activation of) the SCell whose activation is requested by the CU 250 in step S204. The DU 260 may activate the SCell by transmitting an SCell Activation MAC CE to the UE 100 as necessary. The UE 100 activates the SCell (step S206). After the SCell is activated, the DU 260 may return a response to the CU 250 on the F1 interface. In this state, the DU 260 may be prohibited from deactivating the SCell.

[0080] After that, in step S207, it is assumed that the UE 100 is no longer interested in the above MBS service (eg, MBS broadcast).

[0081] In step S208, the UE 100 transmits an MII indicating that the UE 100 is no longer interested in the MBS service to the CU 250. In the case of MBS multicast, the CU 250 may receive information indicating that the UE 100 is no longer interested in the MBS service from the core network.

[0082] In step S209, the CU 250 transmits an F1 message including MBS-related information indicating the release of maintaining the SCell in the active state (i.e., deactivation permission) based on the MII in step S208 (or information received from the core network). The content (items) of the information are the same as those in step S204. The DU 260 deactivates the SCell for which the restriction has been released, as necessary (steps S210 and S211).

[0083] (5) Other embodiments The above-described operational flows are not limited to being implemented independently, but can also be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0084] In the above-described embodiment and example, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB) or a 6G base station. The base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0085] A program may be provided that causes a computer to execute each process performed by UE100 or gNB200 (CU250, DU260). The program may be recorded on a computer-readable medium. The computer-readable medium can be used to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by UE100 or gNB200 may be integrated, and at least a part of UE100 or gNB200 (CU250, DU260) may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0086] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0087] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0088] This application claims priority to U.S. Provisional Application No. 63 / 395933 (filed August 8, 2022), the entire contents of which are incorporated herein by reference.

[0089] (6) Supplementary notes The following additional notes are about the features of the above-described embodiment.

[0090] (Appendix 1) A communication method used in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: a step of transmitting MBS-related information to a distribution unit included in the base station via a network interface between the aggregation unit and the distribution unit, by an aggregation unit included in the base station; The MBS-related information is information about user devices that are receiving or interested in receiving an MBS service provided in a secondary cell under the distributed unit. Communication method.

[0091] (Appendix 2) The network interface is an F1 interface, The step of transmitting the MBS-related information includes the step of transmitting a UE Context Setup Request message including the MBS-related information or a UE Context Modification Request message including the MBS-related information to the distributed unit. 1. A communication method as described in Appendix 1.

[0092] (Appendix 3) The method further comprises receiving, by the aggregation unit, an MBS interest indication from the user equipment, the MBS interest indication being a radio resource control (RRC) message; The step of transmitting the MBS-related information includes the step of transmitting the MBS-related information to the distributed unit based on the MBS interest notification. 3. A communication method according to claim 1 or 2.

[0093] (Appendix 4) The method further comprises the step of the distributed unit determining whether to activate or deactivate the secondary cell for the user equipment based on the MBS-related information received from the aggregation unit. 4. A communication method according to any one of claims 1 to 3.

[0094] (Appendix 5) The method further includes the step of the distributed unit transmitting a Medium Access Control Element (MAC CE) to the user equipment indicating an activation instruction or a deactivation instruction of the secondary cell according to a result of the determination. 4. A communication method as described in Appendix 4.

[0095] (Appendix 6) The MBS-related information is information indicating whether activation of the secondary cell is requested. 6. A communication method according to any one of appendices 1 to 5.

[0096] (Appendix 7) The MBS-related information includes information indicating the reason for the request. 6. A communication method as set forth in Appendix 6.

[0097] (Appendix 8) The MBS-related information includes at least one of information indicating an MBS service that the user device is receiving or is interested in receiving, information indicating an MBS frequency that the user device is receiving or is interested in receiving, and information regarding a cell that provides the MBS service or the MBS frequency. 8. A communication method according to any one of claims 1 to 7.

[0098] (Appendix 9) An aggregation unit included in a base station in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: a transmitter for transmitting MBS-related information to a distributed unit included in the base station through a network interface between the aggregation unit and the distributed unit; The MBS-related information is information about user devices that are receiving or interested in receiving an MBS service provided in a secondary cell under the distributed unit. Aggregation unit.

[0099] (Appendix 10) A distributed unit included in a base station in a mobile communication system providing a multicast / broadcast service (MBS), comprising: a receiving unit for receiving MBS-related information from an aggregation unit included in the base station on a network interface between the aggregation unit and the distribution unit; The MBS-related information is information about user devices that are receiving or interested in receiving an MBS service provided in a secondary cell under the distributed unit. Distributed units. [Explanation of symbols]

[0100] 1: Mobile communication system 10:RAN 20 :CN 100: UE (user equipment) 110: Receiving unit 120: Transmitter 130: Control unit 200:gNB (base station) 210: Transmission unit 220: Receiving unit 230: Control unit 240: Backhaul communication unit 250 CU (aggregate unit) 260: DU (Distributed Unit)

Claims

1. A communication method for use in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: The method includes a step of an aggregation unit included in a network node sending, to a distribution unit included in the network node, a UE Context Setup Request message including MBS-related information or a UE Context Modification Request message including the MBS-related information over an F1 interface between the aggregation unit and the distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Communication method.

2. The method further comprises receiving, by the aggregation unit, an MBS interest indication from the user equipment, the MBS interest indication being a radio resource control (RRC) message; The step of transmitting the MBS-related information includes the step of transmitting the MBS-related information to the distributed unit based on the MBS interest notification. The communication method according to claim 1 .

3. The MBS-related information includes at least one of information indicating an MBS service that the user equipment is receiving or is interested in receiving, information indicating an MBS frequency that the user equipment is receiving or is interested in receiving, and information regarding a cell that provides the MBS service or the MBS frequency. The communication method according to claim 1 .

4. 1. An aggregation unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: a transmitting unit configured to transmit a UE Context Setup Request message including MBS-related information or a UE Context Modification Request message including the MBS-related information to a distributed unit included in the network node via an F1 interface between the aggregation unit and the distributed unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Aggregation unit.

5. 1. A distributed unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: a receiving unit configured to receive, from an aggregation unit included in the network node, a UE Context Setup Request message including MBS-related information or a UE Context Modification Request message including the MBS-related information over an F1 interface between the aggregation unit and the distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Distributed units.

6. A mobile communication system providing a multicast / broadcast service (MBS), comprising: a network node including an aggregation unit and a distribution unit; The aggregation unit sends a UE Context Setup Request message containing MBS-related information or a UE Context Modification Request message containing the MBS-related information to the distribution unit over an F1 interface between the aggregation unit and the distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Mobile communication system.

7. A chipset for controlling an aggregation unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: performing a process of sending a UE Context Setup Request message containing MBS-related information or a UE Context Modification Request message containing the MBS-related information to a distributed unit included in the network node over an F1 interface between the aggregation unit and the distributed unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Chipset.

8. 1. A program for controlling an aggregation unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: causing the aggregation unit to perform a process of sending a UE Context Setup Request message including MBS-related information or a UE Context Modification Request message including the MBS-related information to a distribution unit included in the network node over an F1 interface between the aggregation unit and the distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. program.

9. 1. A chipset for controlling a distributed unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: performing a process of receiving, from an aggregation unit included in the network node, a UE Context Setup Request message including MBS-related information or a UE Context Modification Request message including the MBS-related information over an F1 interface between the aggregation unit and the distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Chipset.

10. 1. A program for controlling a distributed unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: causing the distributed unit to perform a process of receiving, from an aggregation unit included in the network node, a UE Context Setup Request message including MBS-related information or a UE Context Modification Request message including the MBS-related information over an F1 interface between the aggregation unit and the distributed unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. program.

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